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Agar Control TPC for Production and Operator Hands

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Posted 21 September 2020 - 09:07 AM

Hello, we perform agar controls for TPC on our operator workspace. This means that we take imprints of the machines our operators handle (during the break, after mid-production cleaning) and during production we take imprints of the hands and gloves of our operators. The goal is to evaluate their hygienic  working conditions and to correct them when needed.

This procedure was writing long before I was with the company, so I don't have all the rationals for this procedure. I was the first one to take the time and analyse all the scores we have given the past year. I was suprised by how often a low score was given.

Each agar plate is counted and given a score.
After that the average score of our agar plates is determined and an end-score is giving.
However, I feel that the end-score is disproportionately negative and that it is almost impossible to get a good score.



Evaluation for each agar plate:



8,5 cm2              Score               Interpretation


0 t/m 3               0                       Excellent

4 t/m 13             1                       Good

14 t/m 41           2                       Mediocre

41 t/m 130         3                       Insufficiënt

131 or more      4                       Bad


Evaluation average scores:

Score                        Beoordeling

0                                Excellent

0,1 -0,5                      Good

0,6 – 1,5                    Mediocre

1,5 and higher            Bad 


Agar 1  - Excellent - Score 0
Agar 2 - Good - Score 1
Agar 3 - Mediocre - Score 2
Agar 4 - Excellent - Score 0
Agar 5 - Good - Score 1

Total score = 4
Average score = 4/5 = 0,8 = Mediocre. I feel as this score is unfairly low.




Do any of you use a similar procedure? Does any of you have any feedback on our interpretation?

Edited by Simon, 21 September 2020 - 12:23 PM.


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Posted 21 September 2020 - 12:30 PM

It seems to me to be a question of the "purpose" of the overall averaged score? Does it tell you anything useful?
I understand your perspective that a set of result that look nominally quite good sits a little incongruously with an overall score of "mediocre", but equally one could argue that a site/area is only as clean as the least-clean part - I could have an area of the line that was clean to pharmaceutical standards, but that means very little if further down the line is an area with so many bacteria growing that they've formed their own parliament ;)

In that sense, the overall "mediocre" score perhaps reflects this quite well?
(N.B. I'm just musing on the scoring system - not saying your site is dirty!)

The terms allocated to each scoring bracket do of course also make a difference in perception - if the risk here is genuinely relatively low, then perhaps "mediocre" could be swapped for a slightly less pejorative term, e.g. "acceptable".


With the current scoring approach you're somewhat at the mercy of the nature of averages - consider:
Five "good" results gives an averaged score of 1.0, and one could therefore propose that the threshold for "good" should be up to 1.0. However, four excellent results and a "bad" would give an average of 0.8, which would also be "good". Should the overall result be capable of being "good", if one of the results is in the lowest/worst category?


Presumably the overall aim here is to maintain and indeed improve hygiene standards on site, so assuming that the thresholds for the plate counts themselves are valid, you could consider these individually - instead of averaging into a "good", "bad" etc overall score, you could track based on % of tests scoring in each of the categories, with targets for good or better / mediocre or poor, and targets to increase the former. 

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